1. Field of the Invention
The present invention relates generally to apparatus and methods for purging atmospheric air from an enclosed chamber, such as a welding chamber, and replacing the air with an inert gas.
2. Description of Related Art
In the manufacture/repair of complex investment cast shapes for aerospace, medical and land based systems markets, it is oftentimes necessary to perform a welding operation.
For some alloys, particularly titanium alloys, there is a requirement to perform welding in a sealed chamber of argon. In this application, a part is loaded into a chamber and the air is removed by introducing argon to the chamber and expelling the air through mixing/volume exchanges.
The current methodology used to obtain an acceptable inert atmosphere in a chamber or enclosed work area for processes such as welding, an atmosphere with extremely low oxygen, <60 ppm O2 and moisture levels, >−40° F. is obtained as follows. The standard method to purge a non-interlock chamber is to pipe argon into the chamber at a high rate of flow, the argon mixing with the air already in the chamber, which causes both high purity argon and air to be exhausted from the chamber to atmosphere until an acceptable work environment is obtained.
This current production method used to purge large non-interlock welding chambers (e.g. 11′×5′×4′) typically takes a minimum of 8-9 volume changes of argon and 30 plus minutes to obtain an acceptable welding environment. This process wastes large quantities of argon and time (decreases throughput and creates a large amount of idle time).